I posted this to the the guys on the Altair forum also, but I think some guys here have Sol-20 systems...
Apparently the chassis is just brushed Steel on the outside and really just
polished steel on the inside.
When I took mine completely apart I noticed surface rust especially under the
keyboard area. Processor Technologies should have painted or treated it.
Anyway, in poking around the net for some pics, just about every single picture
which showed a Sol-20 with the keyboard cover off has rust forming. There was even a little rust forming underneath the card cage.
If we want to keep our systems for future generations, you may want to check if
you own one and at some point take care of it with some elbow grease and some
fine steelwool. In my case some air tools and some wire wheels, mine was really
I'm debating if I should clear coat it before reassembling, but I guess to keep
it more original I can see if rust forms again now that it's taken care of and
will not be stored in a damp basement but in my office. If it happens again, I
will have to clear coat it.
I'm on a rust removal kick, Apple/Datanetics had the same un-treated steel for
their keyboard support brackets on early Apple II keyboards, I just finished
Rust Treating and sanding out all the rust on mine also.
Anyway just sharing some of my sol discoveries...
Also if anyone needs to replace the black vinyl on the sides, Hobby Lobby sells
sheets of it in a roll for about $8.